Alien "Strangers" whose world is dying collect a group of humans for study in order to find out what makes the heart and mind tick; in solving the mysteries of the human soul, they hope to save themselves. Every night at midnight they erase their subjects' memories and plant new ones - but one man, Murdoch (Rufus Sewell), proves resistant to the experiments and goes on the run, pursued by detective Bumstead (William Hurt) as he falls in love with torch singer Emma (Jennifer Connelly). Working from a script he wrote with Lem Dobbs and David Goyer, director Alex Proyas uses this sci-fi concept to explore the most profound philosophical issues relating to memory, experience and what it means to be human.